White light emitting diode (led) lighting device driven by pulse current

ABSTRACT

A white LED lighting device driven by a pulse current is provided, which consists of blue, violet or ultraviolet LED chips, blue afterglow luminescence materials A and yellow luminescence materials B. Wherein the weight ratio of the blue afterglow luminescence materials A to the yellow luminescence materials B is 10-70 wt %:30-90 wt %. The white LED lighting device drives the LED chips with a pulse current having a frequency of not less than 50 Hz. Because of using the afterglow luminescence materials, the light can be sustained when an excitation light source disappears, thereby eliminating the influence of LED light output fluctuation caused by current variation on the illumination. At the same time, the pulse current can keep the LED chips being at an intermittent work state, so as to overcome the problem of chip heating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/583,464, filed on Nov. 5, 2012. The entirety of which isincorporated herein by reference.

FIELD

The present invention relates to a white LED lighting device usingafterglow characteristic of the luminescence powder and driven by apulse current, which belongs to the field of LED manufacturing. Thepresent invention more particularly relates to a white LED lightingdevice prepared using blue afterglow luminescence materials and yellowluminescence materials.

BACKGROUND

Currently, the LED is used in the fields such as lighting, display,backlight, etc., and as the most promising lighting means of the nextgeneration, the LED gains extensive attention with the advantages ofbeing energy saving, durable, pollution free, etc. There are manysolutions for implementing the white LED, wherein the most maturetechnical solution for preparing the white LED at present is to realizethe white light emission using a combination of the blue LED chip andthe yellow phosphor. Volume 11 page 53 of Appl. Phys. Lett. published in1967 reports a luminescence material Y₃Al₅O₁₂:Ce³⁺, which has a yellowluminescence with a maximum light-emitting wavelength of 550 nm and alife of less than 100 ns. Volume 64 page 417 of Appl. Phys. A publishedin 1997 reports that the white LED light emission is realized using theyellow luminescence of Y₃Al₅O₁₂:Ce³⁺ and the blue gallium nitride, andsuch technology is the most mature technical solution for preparing thewhite LED at present. The existing LED chips are mainly driven by thedirect current having constant magnitude and direction. But in such amode, the LED thermal design requirement is very high, and the LED chipswill be burnt out if the extra heat cannot be dissipated in time.

The Chinese patent No. CN100464111C discloses an alternating current(AC) LED lamp using LED chips of different colors connected in parallelin an AC power source. The patent mainly describes that the LED chips ofdifferent colors together form white light, and recites the specificcircuit such as red, green and blue light emitting chips, withoutmentioning the luminescence powder. The American patent No. U.S. Pat.No. 7,489,086,B2 discloses an AC LED driving apparatus and a lightingdevice using the same. The patent also emphasizes on the circuitstructure without making an innovation report about the luminescencepowder, and the conventional luminescence powder Y₃Al₅O₁₂:Ce³ ⁺ is stillemployed. The inventor of the present invention researches aluminescence material Y₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P having the yellow longafterglow phenomenon and a white LED lighting device driven by a pulsecurrent (the Chinese patent application No. 200910307357.3). However,the white LED lighting device using the pulse current driving mode andthe afterglow characteristic of the luminescence powder to compensatethe light output fluctuation in the present invention is still notreported.

SUMMARY

The objective of the present invention is to provide a white LEDlighting device driven by a pulse current.

The technical solution of the present invention: blue LED chips orultraviolet chips driven by a pulse current+blue afterglow luminescencematerials A+yellow luminescence materials B. Wherein the weight ratio ofthe blue afterglow luminescence materials A to the yellow luminescencematerials B is 10-70 wt %:30-90 wt %, and preferably 20-50 wt%:50-80 wt%. The white LED lighting device drives the LED chips with a pulsecurrent having a frequency of not less than 50 Hz.

The present invention implements a white LED lighting device driven by apulse current, thereby enabling the LED chips to work periodically andintermittently. Meanwhile, the luminescence powder used by the presentinvention has the afterglow effect, which can compensate the lightoutput fluctuation of the lighting device caused by the periodicvariation of the pulse current.

Further, the blue afterglow luminescence material A has a peaklight-emitting wavelength of 440˜490 nm.

Further, the blue afterglow luminescence material A is at least one ofSr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺and CaSrS:Bi³⁺.

The yellow luminescence material B has a peak light-emitting wavelengthof 520˜580 nm.

Further, the yellow luminescence material B is a luminescence materialhaving or not having the afterglow phenomenon, or a combination thereof.

Further, the yellow luminescence material B is at least one ofY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₂O₂S:Mg,Ti, Sr₃SiO₅:Eu²⁺, Dy³⁺,Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Sm³⁺, YAG:Ce and TAG:Ce.

The white light emitted by the white LED lighting device of the presentinvention is formed of the blue light emitted by the blue afterglowluminescence powder, the yellow light emitted by the yellow luminescencepowder and the light from the blue or ultraviolet LED chip under theexcitation of the chip.

The above luminescence powder may also be excited by the violet andultraviolet LED chips, thereby achieving the same effect.

The luminescence coating of the present invention may be formed bymixing the blue afterglow luminescence materials A and the yellowluminescence materials B, or coating the blue afterglow luminescencematerials A on the chips and then coating the yellow luminescencematerials B on the blue afterglow luminescence materials A.

The principle of the white LED lighting device driven by the pulsecurrent in the present invention is as follows:

From the schematic diagram of the basic module of the LED lightingdevice as shown in FIG. 1, it can be seen that due to the pulse periodiccharacteristic of the pulse current, the luminescence of the device alsohas a periodic bright-dark change, i.e., luminescence strobing, therebyinfluencing the usage of the device.

The present invention employs the luminescence materials having theafterglow characteristics so that the light will be sustained when theexcitation light source disappears, thus in the white LED lightingdevice driven by the pulse current based on the solution of the presentinvention, when the current cycle is changed to the small current stage,the blue afterglow material will emit the blue afterglow to compensatethe blue light and excite the yellow luminescence powder, therebyeliminating the influence of the luminescence strobing of the LED chipcaused by the pulse current fluctuation, so that the light output of thedevice during the pulse cycle is kept stable. In addition, since the LEDchip does not work in a half of each pulse cycle, the thermal effectdecreases, which is beneficial to overcome the series of difficultiescaused by chip heating in the usage of the existing white LED lightingdevice. Moreover, the white LED lighting device driven by the pulsecurrent in the present invention achieves a good heat dispersion and along service life without using any complex circuit switching device,which obviously reduces the cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a basic LED lighting device driven by apulse current;

FIG. 2 is an afterglow spectrum of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺;

FIG. 3 is an afterglow spectrum of Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺;

FIG. 4 is a photoluminescence spectrum of Y₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P; andFIGS. 5-1 and 5-2 are schematic diagrams of the structure of an LEDluminescence unit, in FIG. 5-1, 1 denotes a mixed luminescence coatingmade of blue afterglow luminescence materials A and yellow luminescencematerials B; 2 denotes a blue, violet or ultraviolet LED chip; and 3denotes a lens; and in FIG. 5-2, 2 denotes a blue, violet or ultravioletLED chip; 3 denotes a lens; 5 denotes a coating made of blue afterglowluminescence materials A; and 4 denotes a coating made of yellowluminescence materials B.

The above contents of the present invention are further described indetails through the following embodiments in the form of examples. Butit shall be appreciated that the subject scope of the present inventionis not limited to the following examples, and any technology implementedby the above contents of the present invention shall fall within thescope of the present invention. In the examples, the pulse current has afrequency of 100 Hz, the blue LED chip has an emission wavelength of 460nm, the violet LED chip has an emission wavelength of 400 nm, and theultraviolet LED chip has an emission wavelength of 365 nm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A new white LED lighting device consists of blue LED chips, blueafterglow luminescence materials A and yellow luminescence materials B.Wherein the weight ratio of the blue afterglow luminescence materials Ato the yellow luminescence materials B is 10-70 wt %:30-90wt %, andpreferably 20-50 wt %:50-80 wt %. The white LED lighting device drivesthe LED chips with the pulse current having a frequency not less than 50Hz.

Wherein the blue afterglow luminescence material A has a peaklight-emitting wavelength of 440-490 nm, e.g., it may be one orcombinations of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺,CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺ and CaSrS:Bi³⁺.

The yellow luminescence material B may be a luminescence material havingor not having the afterglow phenomenon, or a combination thereof, with apeak light-emitting wavelength of 520-580 nm. The luminescence materialhaving the afterglow phenomenon includes Ce-activatedY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₂O₂S:Mg,Ti, Sr₃SiO₅:Eu²⁺, Dy³⁺,Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ and CaS:Sm³⁺. The luminescence material not havingthe afterglow phenomenon includes YAG:Ce and TAG:Ce.

The white light emitted by the white LED lighting device of the presentinvention is formed of the blue light emitted by the blue afterglowluminescence powder, the yellow light emitted by the yellow luminescencepowder and the light from the blue LED chip under the excitation of theblue LED chip.

The present invention employs the luminescence materials having theafterglow characteristics so that the light will be sustained when theexcitation light source disappears, thus in the white LED lightingdevice driven by the pulse current based on the solution of the presentinvention, when the current cycle is changed, the blue afterglowmaterial will emit the blue afterglow to compensate the blue light andexcite the yellow luminescence powder, thereby eliminating the influenceof the luminescence strobing of the LED chip caused by the pulse currentfluctuation on the illumination, so that the light output of the deviceduring the pulse cycle is kept stable. In addition, since the LED chipdoes not work in a half of each pulse current cycle, the thermal effectdecreases, which is beneficial to overcome the series of difficultiescaused by chip heating in the usage of the existing white LED lightingdevice.

The specific examples are given as follows.

EXAMPLES 1-18

Blue afterglow luminescence Example LED chip material A (wt %) Yellowluminescence material B (wt %) 1 Blue 40%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺60%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P 2 Blue 35%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺65%Y₃Al₅O₁₂: Ce 3 Blue 10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 60%Tb₃Al₅O₁₂: Ce30%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ 4 Blue 5%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ +25%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P + 30%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 10%Sr₃SiO₅:Eu²⁺,Dy³⁺ + 15%CaS: Bi³⁺,Na⁺ 15%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ 5 Blue10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 5%Y₂O₂S: Mg,Ti + 15%CaSrS: Bi³⁺ +25%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P 35%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 5%CaS:Bi³⁺,Na⁺ + 5%CaS: Cu⁺,Na⁺ 6 Blue 5%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 15%Sr₃SiO₅:Eu²⁺,Dy³⁺ + 15%CaSrS: Bi³⁺ + 20%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 20%Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ 25%Y₃Al₅O₁₂: Ce 7 Blue 35%CaS: Bi³⁺,Na⁺ 25%Y₂O₃•Al₂O₃•SiO₂:Ce•B•Na•P + 10%CaS: Sm³⁺ + 15%Y₂O₂S: Mg,Ti + 5%Sr₃SiO₅: Eu²⁺,Dy³⁺ +10%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ 8 Violet 45%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺55%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P 9 Violet 40%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺60%Y₃Al₅O₁₂: Ce 10 Violet 10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 55%Tb₃Al₅O₁₂: Ce35%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ 11 Violet 5%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ +25%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P + 25%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 20%Sr₃SiO₅:Eu²⁺,Dy³⁺ + 15%CaS: Bi³⁺,Na⁺ 10%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ 12 Violet10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 10%Y₂O₂S: Mg,Ti + 10%CaSrS: Bi³⁺ +25%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P 35%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 5%CaS:Bi³⁺,Na⁺ + 5%CaS: Cu⁺,Na⁺ 13 Ultraviolet 40%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺60%Y₃Al₅O₁₂: Ce 14 Ultraviolet 30%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ 70%Tb₃Al₅O₁₂: Ce15 Ultraviolet 20%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 45%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P35%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ 16 Ultraviolet 10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ +30%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P + 25%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 15%Sr₃SiO₅:Eu²⁺,Dy³⁺ + 5%CaS: Bi³⁺,Na⁺ 15%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ 17 Ultraviolet15%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ + 20%Y₂O₂S: Mg,Ti + 5% CaSrS:Bi³⁺ +40%Y₂O₃•Al₂O₃•SiO₂: Ce•B•Na•P 10%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ + 5%CaS:Bi³⁺,Na⁺ + 5%CaS: Cu⁺,Na⁺ 18 Ultraviolet 10%Sr₂MgSi₂O₇: Eu²⁺,Dy³⁺ +15%Sr₃SiO₅: Eu²⁺,Dy³⁺ + 5%CaSrS: Bi³⁺ + 15%Ca₂MgSi₂O₇: Eu²⁺,Dy³⁺ +35%Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ 20%Y₃Al₅O₁₂: Ce

The preparation method is as follows: 500-mesh-screening luminescencematerials A and B, uniformity mixing the luminescence materials A and Bin the ratios described in Examples 1-18, and packing them with an LEDchip having the power of 0.1 W, so as to form a white LED lightingdevice with its basic unit as shown in FIG. 1, and the pulse current hasa frequency of 100 Hz.

TEST EXAMPLE 1 Luminescence Characteristics of the LED Lighting Deviceof the Present Invention

The pulse current used in the present invention has a frequency of 100Hz, i.e., the cycle is 10 ms. Table 2 gives the brightness within 20 mstested by the lighting device shown as the module in FIG. 1 with ahigh-speed camera shooting 300 photos per second, when the LED chipsgiven in Examples 1-18 are directly powered by the AC mains supply. Thereference sample is an LED lighting device driven by a pulse currentformed in the same manner with a white LED chip having the commerciallyavailable blue chip packed with the yellow luminescence material. Thebrightness data in Table 2 is the relative test brightness of theinstrument and has no dimension.

TABLE 2 Time 3.33 6.66 9.99 13.32 16.65 19.98 ms ms ms ms ms msBrightness of 3565 3466 69 3253 3570 81 Reference sample Brightness of3436 3425 1835 3487 3500 1916 example 1 Example 2 3160 3230 1760 29803123 1783 Example 3 2786 2963 1600 2935 2963 1562 Example 4 2790 29001652 2723 2845 1593 Example 5 2543 2669 1512 2711 2814 1612 Example 62621 2736 1650 2789 2698 1701 Example 7 2317 2423 1502 2504 2642 1490Example 8 2793 2851 1711 2860 2894 1723 Example 9 2714 2802 1250 27322800 1196 Example 10 2316 2631 1436 2403 2532 1399 Example 11 2588 27231563 2711 2733 1600 Example 12 2222 2434 1436 2412 2436 1283 Example 132633 2749 1504 2737 2765 1490 Example 14 2763 2810 1477 2677 2714 1511Example 15 2454 2671 1512 2555 2545 1563 Example 16 2637 2697 1400 27102721 1507 Example 17 2332 2431 1365 2412 2455 1400 Example 18 2679 27881566 2757 2800 1571

As can be seen from the data in Table 2, the luminescence of the presentinvention is stable during the pulse current cycle, while theluminescence of the white LED lighting device using the commerciallyavailable blue chip packed with the conventional yellow YAG luminescencematerial having no afterglow is unstable, and fluctuates very obviouslyduring the pulse current cycle.

TEST EXAMPLE 2 Light Attenuation of the LED Lighting Device of thePresent Invention

Table 3 shows the light attenuation data of Examples 1-18 and thereference sample. The reference sample is a lighting device formed byinstalling the white LED chip having the commercially available bluechip packed with the yellow luminescence material in the general directcurrent (DC) power supply mode at present. The test method is asfollows: powering on the LED lighting devices driven by the pulsecurrent of Examples 1-18 and the reference sample, and testing theirbrightness at a certain interval. The results are shown in Table 3,wherein the data is relative brightness and normalized with the initialdata.

TABLE 3 Time 1 h 1000 h 1500 h 2500 h Brightness of 100 98 97 94Reference sample Brightness of 100 99.8 99.3 99.2 example 1 Example 2100 99.5 99.2 99 Example 3 100 99.5 99 98 Example 4 100 99.7 99.3 99Example 5 100 99.8 99.4 98.6 Example 6 100 99.5 99 98 Example 7 100 99.499 98.3 Example 8 100 99.7 99.2 99 Example 9 100 99.5 99 98 Example 10100 99.6 99 98.6 Example 11 100 99.5 99 98 Example 12 100 99.3 99 98.2Example 13 100 99.5 99 98 Example 14 100 99.6 99.1 98 Example 15 10099.5 99 98 Example 16 100 99.8 99.2 99 Example 17 100 99.4 99.1 98.5Example 18 100 99.5 99.3 98.4

As can be seen from the data in Table 3, the brightness attenuation ofthe white LED lighting device driven by the pulse current of the presentinvention is less than that of the LED lighting device using theexisting mode.

The data of Tables 2-3 indicates that the white LED lighting devicedriven by the pulse current prepared with the afterglow luminescencematerials in the present invention is advantageous in stableluminescence and small light attenuation, thereby having obvious noveltyand inventiveness over the existing LED lighting device.

1-20. (canceled)
 21. A method of using a white LED lighting device,comprising: connecting a white LED lighting device to a power source,wherein the white LED lighting device comprises blue, violet orultraviolet LED chips and luminescence material, the luminescencematerial being a combination of blue afterglow luminescence material Aand yellow luminescence material B, the yellow luminescence material Bbeing able to emit light under excitation of the blue, violet orultraviolet LED chips and/or excitation of the blue afterglowluminescence material A, a weight ratio (A:B) between the blue afterglowluminescence material A and the yellow luminescence material B being10˜70 wt %:30˜90 wt %; and providing a pulse current having a frequencyof not less than 50 Hz to drive the LED chips to generate a white LEDlight.
 22. The method of claim 21, wherein the weight ratio (A:B)between the blue afterglow luminescence material A and the yellowluminescence material B is 20˜50 wt %:50˜80 wt %.
 23. The method ofclaim 21, wherein the weight ratio (A:B) between the blue afterglowluminescence material A and the yellow luminescence material B is 35˜50wt %:50˜65 wt %.
 24. The method of claim 21, wherein the weight ratio(A:B) between the blue afterglow luminescence material A and the yellowluminescence material B is 40˜50 wt %:50˜60 wt %.
 25. The method ofclaim 21, wherein the blue afterglow luminescence material A has a peaklight-emitting wavelength of 440˜490 nm.
 26. The method of claim 21,wherein the yellow luminescence material B has a peak light-emittingwavelength of 520˜580 nm.
 27. The method of claim 21, wherein the blueafterglow luminescence material A comprises one or more materialsselected from the group consisting of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺,Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺ and CaSrS:Bi³⁺.
 28. Themethod of claim 31, wherein the yellow luminescence material B comprisesone or more materials selected from the group consisting ofY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce, Y₂O₂S:Mg,Ti,Sr₃SiO₅:Eu²⁺,Dy³⁺, Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Sm³⁺, YAG:Ce and TAG:Ce.29. The method of claim 21, wherein the yellow luminescence material Bis a yellow luminescence material with or without an afterglowphenomenon, or a combination thereof.
 30. The method of claim 21,wherein the blue afterglow luminescence material A comprises one or morematerials selected from the group consisting of Sr₄Al ₁₄O₂₅:Eu²⁺,Dy³⁺,Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺ and CaSrS:Bi³⁺, andwherein the yellow luminescence material B comprises one or morematerials selected from the group consisting ofY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce, Y₂O₂S:Mg,Ti,Sr₃SiO₅:Eu²⁺, Dy³⁺, Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺, CaS:Sm³⁺, YAG:Ce and TAG:Ce.31. A method of producing LED light, comprising: mixing a blue afterglowluminescence material A with a yellow luminescence material B to form amixture, wherein the yellow luminescence material B is able to emitlight under excitation of the blue, violet or ultraviolet LED chipsand/or excitation of the blue afterglow luminescence material A, whereinthe blue afterglow luminescence material A and the yellow luminescencematerial B is mixed at a weight ratio (A:B) of 10˜70 wt %:30˜90 wt %;packing or coating at least one blue, violet or ultraviolet LED chipwith the mixture; and providing a pulse current having a frequency ofnot less than 50 Hz to drive the LED chips to generate a white LEDlight.
 32. The method of claim 31, wherein the weight ratio (A:B)between the blue afterglow luminescence material A and the yellowluminescence material B is 20˜50 wt %:50˜80 wt %.
 33. The method ofclaim 31, wherein the weight ratio (A:B) between the blue afterglowluminescence material A and the yellow luminescence material B is 35˜50wt %:50˜65 wt %.
 34. The method of claim 31, wherein the weight ratio(A:B) between the blue afterglow luminescence material A and the yellowluminescence material B is 40˜50 wt %:50˜60wt %.
 35. The method of claim31, wherein the blue afterglow luminescence material A has a peaklight-emitting wavelength of 440˜490 nm.
 36. The method of claim 31,wherein the yellow luminescence material B has a peak light-emittingwavelength of 520˜580 nm.
 37. The method of claim 31, wherein the blueafterglow luminescence material A comprises one or more materialsselected from the group consisting of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺,Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺ and CaSrS:Bi³⁺.
 38. Themethod of claim 31, wherein the yellow luminescence material B comprisesone or more materials selected from the group consisting ofY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce, Y₂O₂S:Mg,Ti,Sr₃SiO₅:Eu²⁺,Dy³⁺, Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Sm³⁺, YAG:Ce and TAG:Ce.39. The method of claim 31, wherein the yellow luminescence material Bis a yellow luminescence material with or without an afterglowphenomenon, or a combination thereof.
 40. The method of claim 31,wherein the blue afterglow luminescence material A comprises one or morematerials selected from the group consisting of Sr₄Al ₁₄O₂₅:Eu²⁺,Dy³⁺,Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Bi³⁺,Na⁺, CaS:Cu⁺,Na⁺ and CaSrS:Bi³⁺, andwherein the yellow luminescence material B comprises one or morematerials selected from the group consisting ofY₂O₃.Al₂O₃.SiO₂:Ce.B.Na.P, Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce, Y₂O₂S:Mg,Ti,Sr₃SiO₅:Eu²⁺,Dy³⁺, Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺, CaS:Sm³⁺, YAG:Ce and TAG:Ce.